⚡ Optimize logarithmicScale with LUT #31
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Optimized the `logarithmicScale` function in `src/core/utility/utility.cpp` by introducing a precomputed Lookup Table (LUT) for the most common scale factors (0 to 4). The previous implementation relied on a loop that repeatedly called `std::log10`, which was a significant bottleneck in the spectrum analyzer's rendering path. Key changes: - Defined a static LUT with 16,384 entries for scale factors 0-4. - Implemented a thread-safe static initializer to populate the LUT on first use. - Replaced the loop with a fast nearest-neighbor lookup for scale factors < 5. - Provided a fallback loop for scale factors >= 5 to maintain full functionality. Performance results (from standalone benchmark): - f=1: ~21ns -> ~4.6ns (~4.5x faster) - f=2: ~41ns -> ~4.7ns (~8.7x faster) - f=4: ~100ns -> ~5.7ns (~17.5x faster) Accuracy: The 16,384 entry LUT ensures a maximum error of ~0.0048 for f=4, which corresponds to less than 2 pixels of error on a typical 350-pixel high spectrum display, making the optimization visually indistinguishable from the original calculation. Co-authored-by: segin <[email protected]>
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This PR optimizes the
logarithmicScalefunction insrc/core/utility/utility.cppto improve the performance of the spectrum analyzer visualization.💡 What:
Replaced the iterative
std::log10loop inlogarithmicScalewith a precomputed Lookup Table (LUT) for scale factors 0 through 4. A LUT size of 16,384 entries was chosen to balance memory usage (approx. 320 KB total) and precision.🎯 Why:
The
logarithmicScalefunction is a "hot" function called hundreds of times per frame (e.g., once for each frequency bin in the spectrum analyzer). The original implementation's use of repeated transcendental function calls was inefficient.📊 Measured Improvement:
Benchmarking showed significant speedups across all common scale factors:
Precision remains very high, with a maximum error of approximately 0.0048 for the most aggressive scaling (f=4), which is well within the acceptable range for UI visualizations.
Existing functionality is preserved for all inputs, with a safe fallback loop for scale factors >= 5.
PR created automatically by Jules for task 11172138513976651972 started by @segin